The present invention relates to an absorbent structure containing loosely compacted cellulosic fibers, which structure is particularly suitable for use in absorbent products requiring a substantial liquid holding capacity.
Absorbent structures such as disposable diapers, sanitary napkins, incontinent pads and the like are generally structured so as to have a facing sheet which is moisture permeable, an absorbent batt which has a high liquid holding capacity and a backing sheet which is moisture impervious. For any absorbent structure to be satisfactory, it is highly desirable for the structure to (1) readily accept liquid (2) easily transport the liquid from one portion of the structure to another and (3) hold the liquid accepted. The facing sheet mentioned above must permit the liquid to penetrate the facing to reach the absorbent batt. The backing sheet keeps the liquid from leaking and therefore must be moisture impermeable. The present invention relates to an improvement in the absorbent batt used for these absorbent structures.
Conventionally, loosely compacted cellulosic fibrous batts are of substantially rectangular shape and are made by air laying wood pulp fibers, cotton linters or the like, on a foraminous support. The batt may be laid in a prescribed shape or may be shaped subsequent to the air laying of the fibers. These batts are incorporated by various techniques into products such as disposable diapers, sanitary napkins, incontinent pads and the like. Various techniques have been developed or suggested for improving the absorbent characteristics of the absorbent batts and to improve the liquid transporting characteristics, i.e., wicking characteristics. For instance, U.S. Pat. No. 3,017,304 to Burgeni teaches forming a paper-like densified skin on one surface of the absorbent batt. The skin assists in transporting the liquid and lends integrity to the batt. In another instance, U.S. Pat. No. 3,938,522 to Repke suggests densifying portions of the batt to both assist in transporting of liquid and strengthening the absorbent batt. Previously, in each instance when a portion or portions of the absorbent batt have been densified, liquid holding capacity has been reduced and those densified portions are rigid and have a tendency to break when the batt is flexed. As mentioned above, for any absorbent structure to be satisfactory, it is not only necessary for the structure to hold liquid, but also to readily accept liquid and transport it. The liquid holding capacity of the absorbent structure relates to the pore size of the fibrous bed. If the pore size (i.e., the spaces surrounding the fibers) is large, then the structure will have a relatively high liquid holding capacity but generally does not accept and transport liquid readily. On the other hand, if the pore size is smaller, the structure readily accepts and wicks liquid but may have a lower liquid holding capacity.